The present invention relates to a material testing apparatus, and more particularly, a micro-material testing apparatus which conducts material tests for superfine materials and ultra thin film materials used for semiconductor devices, such as a micro-machine or LSI.
A material testing apparatus for evaluating a material strength applies a load to a test member to displace the same so as to conduct material strength tests, such as tensile test, compression test, bending test and torsion test. In the conventional material testing apparatus, a driving mechanism, such as air pressure, oil pressure, motor solenoid or the like, has been used as load applying means for applying a load.
In the driving means using air pressure, oil pressure, motor, solenoid or the like, which is provided in the conventional material testing apparatus, it is difficult to slightly control a load amount and a displacement amount to be applied. Therefore, it is difficult to apply a minute load and to provide a small displacement, so that the strength of a micro-material can not be measured accurately. Accordingly, it has been a problem that the conventional material testing apparatus is not suitable for a micro-material test.
Also, the test member, which is an object to be measured in the conventional material testing apparatus, is a block member having a certain thickness. Therefore, it has been a problem that the conventional material testing apparatus can not evaluate a peeling strength of a thin film by applying an additional load only to the thin film.
Further, in the conventional material testing apparatus, fixation of the test member is made by a holding mechanism which mechanically holds the test member. Thus, it has been a problem that this mechanical holding mechanism can not hold the test member securely in case the test member is a micro-material.
The present invention has been made to solve the above problems of the conventional apparatus, and an object of the present invention is to provide a micro-material testing apparatus which can measure a strength of a micro-material.
Another object of the present invention is to provide the micro-material testing apparatus as stated above, which can measure a peeling strength of a thin film material.
A further object of the present invention is to provide a method for securely holding a micro-material.
Further objects and advantages of the invention will be apparent from the following description of the invention.
To achieve the above objects, the present invention provides a micro-material testing apparatus which conducts a strength test of the micro-material, and the present invention also provides a method for securely holding the micro-material. A mechanism, which is provided in an atomic force microscope and is designed to move a probe for a small amount in order to measure a shape, is diverted as means for slightly moving a micro-material for a material test and applying a minute load thereto. The atomic force microscope is known and is disclosed in, for example, U.S. Pat. No. 4,724,318, RE 33,387 and Japanese Patent Publication (KOKOKU) 7-54249.
The micro-material testing apparatus of the present invention has two embodiments in accordance with variations of applying minute displacement and a minute load to a micro-material, and also has an embodiment in case a micro-material is a thin film.
A first embodiment of the micro-material testing apparatus is formed such that in a cantilever, moving means and displacement detecting means, which are provided in an atomic force microscope, a test member is provided instead of the cantilever, the moving means is used as load applying means for applying a load to the test member, and the displacement detecting means detects a displacement of the test member, so that a material test for the test member is conducted based on a load amount and a displacement amount.
The first embodiment of the micro-material testing apparatus has a structure such that the test member is attached instead of the cantilever in the atomic force microscope, and a sample to be placed in the microscope is used as a sample table. Then, the moving means, which is normally used for moving the cantilever or the sample in accordance with a shape of the sample, is used as load applying means for applying the load to the test member. Thus, the minute displacement or load can be applied to the test member.
Also, a second embodiment of the micro-material testing apparatus is formed such that in a cantilever, moving means and displacement detecting means, which are provided in an atomic force microscope, the moving means and the cantilever constitute load applying means for applying a load to the test member, and displacement of the test member is detected by the displacement detecting means, so that a material test for the test member is conducted based on the load amount and the displacement amount.
The second embodiment of the micro-material testing apparatus has a structure such that a portion of the cantilever in the atomic force microscope constitutes a member for applying the load to the test member, and the moving means, which is normally used for moving the cantilever or the sample in accordance with the shape of the sample, is used as load applying means for applying a load to the test member. Therefore, minute displacement or load can be applied to the test member.
Further, a third embodiment of the micro-material testing apparatus is formed such that in a cantilever, moving means and displacement detecting means, which are provided in an atomic force microscope, the moving means and the cantilever constitute load applying means for applying a load to a thin film test member, and displacement of the test member is detected by the displacement detecting means, so that a peeling test for the thin film test member is conducted based on the load amount and the displacement amount.
The third embodiment of the micro-material testing apparatus has a structure such that a portion of the cantilever in the atomic force microscope constitutes a member for providing a tension to the thin film test member, and the moving means, which is normally used for moving the cantilever or the sample in accordance with a shape of the sample, is used as load applying means for providing the tension to the thin film test member. Therefore, minute displacement or load in a tensile direction can be applied to the thin film test member.
Incidentally, the moving means of the present invention has a mechanism which relatively changes the positions of the sample and the cantilever in the atomic force microscope, and for example, it may be a three-dimensional actuator using a piezoelectric element.
The displacement amount of the test member can be measured by the displacement detecting means. The amount of the load applied to the test member is assumed from the displacement amount and modulus of longitudinal elasticity so that breaking strength of the micro-material can be evaluated. Also, in case the load applying means is formed of the three-dimensional actuator using the piezoelectric element, by determining in advance a relationship between an applied voltage and a load to be generated, the applied load can be assumed from the applied voltage.
Also, by using the measured displacement amount, stress inside the test member can be evaluated by employing a beam theory or a finite element method.
The micro-material testing apparatus can conduct various kinds of tests, such as tensile test, compression test, bending test and torsion test depending on a direction of applying a load by the moving means and an arrangement of the test member.
Also, in the micro-material testing apparatus of the present invention, depending on the contents of the material test, it is necessary to fix the cantilever to the micro-material. In this case, according to the present invention, electricity is applied between the cantilever and the micro-material contacting the cantilever, and a portion of the micro-material contacting the cantilever is fused by heat generated by applying electricity, so that the cantilever is fixed to the micro-material by fusion of the portion of the micro-material. Therefore, the micro-material can be fixed stably and securely.